# Line/curve with expression from two data tables

Hello,

I'm to make a combination chart (bar and line) in version 7.12 to show scrap dollars as a percent of sales by month. I have two data tables, one with scrap transactions by dollar and date, and the other with sales by date. These tables aren't really related other than date in this example.

I'm having difficulty figuring out the formula for the expression or if it's even possible to do so. The formula would be [Total_Scrap] / [Total_Sales] for each month, but I'm unable to select these two data tables in the custom expression.

Below are examples from Excel and then where I think the formula would go in Spotfire.

Any ideas or suggestions would be much appreciated.

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